1. Field of the Invention
The present invention relates to flow meter type identification, and more specifically to flow meter type identification using meter calibration values.
2. Statement of the Problem
Flow meters are used to measure the mass flow rate of flowing liquids. Many types of flow meters exist and accommodate a variety of applications and flowing materials. For example, there may be different flow meter types/models for different flowtube line sizes, tube materials, pressure ratings, temperature ratings, accuracy ratings, etc. Each flow meter type may have unique characteristics which a flow meter system must account for in order to achieve optimum performance. For example, some flow meter types may require a flowtube apparatus to vibrate at particular displacement levels. In another example, some flow meter types can require special compensation algorithms.
Flow meter electronics typically include stored meter calibration values. The flow meter uses these meter calibration values in order to accurately measure mass flow rate and density. The meter calibration values can comprise calibration values derived from measurements under test conditions, such as at the factory. Therefore, each flow meter can have unique calibration values.
One type of flow meter is a Coriolis flow meter. It is known to use Coriolis mass flow meters to measure mass flow and other information of materials flowing through a pipeline as disclosed in U.S. Pat. No. 4,491,025 issued to J. E. Smith, et al. of Jan. 1, 1985 and Re. 31,450 to J. E. Smith of Feb. 11, 1982. These flow meters have one or more flow tubes of different configurations. Each conduit configuration may be viewed as having a set of natural vibration modes including, for example, simple bending, torsional, radial and coupled modes. In a typical Coriolis mass flow measurement application, a conduit configuration is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at points spaced along the conduit. The vibrational modes of the material filled systems are defined in part by the combined mass of the flow tubes and the material within the flow tubes. When there is no material flowing through the flow meter, all points along a flow tube oscillate with an identical phase. As a material begins to flow through the flow tube, Coriolis accelerations cause each point along the flow tube to have a different phase with respect to other points along the flow tube. The phase on the inlet side of the flow tube lags the driver, while the phase on the outlet side leads the driver. Sensors are placed at different points on the flow tube to produce sinusoidal signals representative of the motion of the flow tube at the different points. A phase difference of the signals received from the sensors is calculated in units of time. The phase difference between the sensor signals is proportional to the mass flow rate of the material flowing through the flow tube or flow tubes.
The mass flow rate of the material is determined by multiplying the phase difference by a Flow Calibration Factor (FCF). Prior to installation of the flowmeter into a pipeline, the FCF is determined by a calibration process. In the calibration process, a fluid is passed through the flow tube at a given flow rate and the relationship between the phase difference and the flow rate is calculated (i.e., the FCF). The flow meter subsequently determines a flow rate by multiplying the FCF by the phase difference of the two pickoff signals. In addition, other calibration factors can be taken into account in determining the flow rate.
Many flow meter applications comprise a flow meter network that includes multiple individual flow meters operating within a communication network of some manner. The network commonly includes a flow meter monitoring system that gathers measured flow data and controls and coordinates operations of various flow meters. The flow meter network may include flow meters of different sizes, models, model years, and electronics and software versions. In such a setting, it is desirable that the flow meter type be easily and automatically identified so that maintenance and upgrading procedures can be efficiently and properly performed.
When electronic flow meters were initially developed, the identification and tracking of flow meter type was not an issue. This was due to the relatively few flow meter manufacturers and few flow meter models. As a result, manual tracking and record-keeping of flow meter types was easy. However, it is impossible to design flow meters without designing for unique characteristics for specific and varying applications and while yet achieving lower costs, higher performance, smaller footprints, and other aspects desirable of a flow meter. As a result, the number of flow meter types has proliferated in order to suit specific and wide-ranging needs.
One prior art approach requires a user to enter the sensor model/type into a flow meter monitoring device, such as by entering a code or identifier. This approach is acceptable if the person doing the entering is knowledgeable about flow meters and flow meter types. However, this prior art approach has drawbacks. This prior art approach relies on the person doing the entering to have at least some familiarity with flow meter types, relies on the person to know how to input data into the transmitter or monitoring device, and relies on complete, error-free, and accurate entry of the code or identifier.
Another prior art approach has been to include a memory device in a flow meter. The memory stores a flow meter type data as a readable code or identifier. A remote flow meter monitoring system can query the memory to obtain the flowmeter type code or identifier. However, this prior art approach also has drawbacks. A memory device is a significant cost addition to a flow meter. In addition, the memory device, such as a solid state memory, is a relatively fragile device that is not suited for inclusion in a high temperature and high vibration environment of a flow meter.
Yet another prior art approach is the inclusion of a resistor into a flow meter, wherein the resistor generates a relatively unique electrical voltage/current response that is remotely read. A resistor is an inexpensive and robust device that can be easily integrated into a flow meter. However, this prior art approach also has drawbacks. The increasing number of flow meter types necessitates the use of smaller and smaller resistance ranges to delineate each flow meter model. This leads to uncertainties when the resistance tolerance is critical. In addition, global flowmeter type identification would require coordination between flow meter manufacturers.
Yet another prior art approach is to induce an initial vibration of the subject flow meter and measure the resulting frequency of vibration of the flowtube. The resulting vibration frequency is then correlated to a flow meter type. However, this prior art approach also has drawbacks. The vibration test must be properly conducted and the flow meter has to be set to the appropriate test conditions. Further, the test may result in a measured response vibration that doesn't fully indicate the flow meter type. Flow meter tolerance variations, together with variations in the ambient conditions, may result in an incorrect flowmeter type determination.